Dormancy and sprouting of bulbs in Oxalis ladfolia H.B.K. and O. pes-caprae L.

A series of laboratory experiments was made to find a reliable and quick method of terminating the dormancy of bulbs of Oxalis lalifolia H.B.K. and Oxalis pes-caprae L. It was found that the dormant period of the bulbs of O. latifoliti could be terminated by chilling al 5°C for 3 weeks followed by dry heating at 45°C for 4 h and then moist storage at 23°C. The dormancy of bulbs of O. pes-caprae was overcome by chilling them for 6 weeks in polyethylene bags at temperatures between 2and 10°C and then storing without added moisture in polyethylene bags at 20°C. Some physiological and ecological aspects of the work arc discussed. Dormance et germination des bulbes d'Oxalis latifolia H.B.K. et d'O. pes-caprae L. Une série d'expériences de laboratoire a été réealisée pour rechercher une méthode süre et rapide pour rompre la dormance des bulbes d'OxaHs latifolia K.B.K. et d'Oxalis pes-caprae L. II a été constaté que Ton pouvait mellre fin à la période de dormance des bulbes d'O. latifolia par un refroid-issement à 5° C pendant 3 semaines, suivi d'un chauffage à sec à 45°C pendant 4 heures. puis d'une conservation en atmosphere humide à 23°C. La dormance des bulbes d'O. pes-caprae a été rompue par exposition au froid pendant 6 semaines dans des sacs de polyethylene à des températures comprises entre 2° et 10°C et en les conservant sans les humidifier en sacs de polyéthylene à 20°. Certains aspects physiologiques et écotogiques de cc travail sont discutés. Dormanz und Austrieb der Zwiebeln von Oxalis latifolia H.B.K. undo, pes-caprae L. Es wurde eine Reihe von Laboruntersuchungen durchgeführt, um ein zuverlässiges und schnelles Verfahren zur Brechung der Dormanz der Zwiebeln von Oxalis latifolia H.B.K. und Oxalis pes-caprae L. zu linden. Dabei wurde herausgefunden. dass die Dormanz der Zwiebein von O. latifolia durch dreiwöchige Lagerung bei 5°C, gefolgt von einem vierstündigen Trocknen bei 45°C und anschliessender feuchter Lagerung bei 23°C, gebrochen werden kann. Bei O.pes-caprae wurde die Dormanz der Zwiebein wie folgt gebrochen: Sechs Wochen Lagerung in Polyäthylenbeuteln bei 2 10°C und Aufbewahrung ohne Zusatz von Feuchtlgkeit bei 20°C in Polyäthylenbeuteln. Einige physiologische und ökologische Gesichtspunkte der Arbeit werden besprochen.     

PCR-based differentiation of Fusarium oxysporum ff. sp. lycopersici and radicis-lycopersici and races of F. oxysporum f. sp. lycopersici

The pathogenic type (form and race) of Fusarium oxysporum, which generates wilt symptoms on tomato, was rapidly identified with a polymerase chain reaction (PCR)-based technique. We compared the partial nucleotide sequences of endo polygalacturonase (pg1) and exo polygalacturonase (pgx4) genes from isolates of F. oxysporum ff. sp. lycopersici (FOL) and radicis-lycopersici (FORL) from Japan and designed specific primer sets (uni, sp13, sp23, and sprl) based on the nucleotide differences that appeared among the pathogenic types. PCR with the uni primer set amplified a 670∼672-bp fragment from all isolates of FOL and FORL. With the sp13 primer set, an amplicon of 445 bp was obtained only from isolates of FOL race 1 and 3. With the sp23 primer set, a 518-bp fragment was obtained from isolates of FOL race 2 and 3. The sprl primer set yielded a 947-bp fragment from isolates of FORL, but not from FOL. A combination of amplifications with these primer sets effectively differentiated the pathogenic types of F. oxysporum in tomato.     

Interactions between Fusarium oxysporum f. sp. tracheiphilum and Meloidogyne spp. in Vigna unguiculata. 3. Pathogenesis by F. o. tracheiphilum as affected by M. javanica and host cultivar

Experiments were conducted to determine the temporal and spatial effects of Meloidogyne jav anica and host cultivar on pathogenesis by Fusarium oxysporum f. sp tracheiphilum in cowpea. In the wilt-susceptible cowpea cultivar California Blackeye No. 5 (CB5). F. o. tracheiphilum proliferated rapidly in both the hypocotyl and first internode 6 weeks after inoculation. The fungus spread quickly upward as plants grew, colonized most tissues within 6 weeks, and caused severe wilt. In wilt-resistant cultivar CB3. there was little proliferation of F. oxysporum in any tissue, whether or not plants were infected by St. javanica. The fungus was found above the primary internode in 15"., of all CB3 plants, but did not continue to spread upward after 4 weeks Vascular discoloration was greatest when St. javanica was added 4 weeks before F. o. tracheiphilum, but simultaneous inoculation also increased wilt symptoms Root wounding did not increase wilt. Split-root experiments provided no evidence that infection by, M. javanica results in a translocatable factor that reduces wilt resistance. When hypocoivls were inoculated with F. o. tracheiphilum at different intervals after roots infected by St. jav anica were removed, there was no evidence that the effect of the nematode on wilt susceptibility was translocated or persistent.     

Genetic Relatedness among Pseudomonas avellanae, P. Syringae pv. Theae and P.s. pv. Actinidiae, and their Identification

A total of 37 strains of Pseudomonas avellanae, P. syringae pv. theae and P.s. pv. actinidiae, including pathotype and reference strains, obtained from all the countries where these pathogens have been reported, were compared by means of ARDRA, repetitive PCR using ERIC, BOX and REP primer sets, whole-cell protein analysis, biochemical and nutritional tests, and pathogenicity tests. P. syringae pathovar type strains representing six genomospecies sensu Gardan et al. (1999), were also included for comparison in UPGMA cluster analysis of repetitive PCR data and SDS-PAGE of protein extracts. Among the 12 endonucleases used in ARDRA, only Tru 9I differentiated P. avellanae from P.s. pv. theae and P.s. pv. actinidiae. UPGMA cluster analysis of repetitive PCR genomic fingerprints showed 65% similarity between P.s. pv. theae and P. avellanae and 50% between the latter species and P.s. pv. actinidiae. Strains of P.s. pv. actinidiae could be grouped according to their geographic origin. Similar results were obtained with SDS-PAGE cluster analysis. PCR amplification using primers PAV 1 and PAV 22 that were developed to detect P. avellanae in apparently healthy and visibly infected hazelnut specimens yielded a band of 762bp from all strains of P. avellanae, P.s. pv. theae and P.s. pv. actinidiae. All strains lacked the syrB gene. Based on these data, we suggest that P.s. pv. actinidiae should be included in the genomospecies 8 together with P. avellanae and P.s. pv. theae. Selected biochemical and nutritional tests could differentiate these groups of strains. Pathogenicity tests clearly indicated that each group is specifically pathogenic only on the host plant species from which it was originally isolated.The author is staff member of the Istituto Sperimentale per la Patologia Vegetale, Roma, Italy temporarily assigned to ISF.     

Fenbendazole. II. Biological properties and activity

Fenbendazole has a broad spectrum of activity against immature and adult helminths of the intestinal tract and lungs at an oral dose of 5–7.5 mg/kg. This compound has a wide margin of safety in domestic animals without teratogenic side effects. Data are given on metabolism, mode of action and excretion.     

醉蝶白粉病的发生规律与防治

研究明确醉蝶白粉病菌以闭囊壳、分生孢子和菌丝在病残体上或土壤中越冬。醉蝶开花至盛花期为发生高峰期 ,高温干燥的气候条件发病严重。发生程度与土壤肥力、田间种植密度等关系密切。加强管理 ,清洁田园和30%特富灵、6%乐必耕、75%百菌清、25%粉锈宁可湿性粉剂等在定植后、开花前后喷药 ,每隔10d1次 ,连续5～6次 ,可基本控制该病发生。     

Attempted somatic hybridization of Puccinia striiformis f. sp. tritici and P. striiformis f. sp. hordei

Attempts were made to produce somatic hybrids between isolates of Puccinia striiformis f. sp. tritici and f. sp. hordei. A mixed infection was produced on a common susceptible barley host, Fong Tien, using white-spored isolates of P. striiformis f. sp. tritici and yellow-spored isolates off. sp. hordei. Selection was made for non-parental spore colour on selective wheat and barley hosts, and variants thus isolated were analysed for virulence markers, and for isozyme and double-stranded RNA (dsRNA) markers, all of which clearly differentiated the parental isolates. Two white-spored (non-parental) isolates were found on the selective barley host which otherwise resembled the parental f. sp. hordei isolate in virulence, isozyme and dsRNA markers. The most likely explanation of the origin of these isolates is mutation to white spore colour in the f. sp. hordei isolate.     

Pythium uncinulatum sp. nov. and P. tracheiphilum pathogenic to lettuce

From mature lettuce heads with bottom rot symptoms severalPythium species were isolated, two of which were studied further. Pathogenicity tests with both fungi have been carried out only with seedlings. P. uncinulatum sp. nov. was isolated frequently. Its relation to otherPythium spp. with spiny oogonia is discussed. It proved to be very pathogenic to seedlings of lettuce and somewhat less to those of cucumber and tomato. P. tracheiphilum, which was isolated far less frequently, proved to be highly pathogenic to seedlings of lettuce, cucumber and cauliflower, and somewhat less to tomato and pea.Samenvatting Van slaplanten met smetsymptomen werden behalveBotrytis cinerea, Rhizoctonia sp. enSclerotinia spp. dikwijlsPythium-soorten geïsoleerd. Twee hiervan zijn nader onderzocht. P. uncinulatum (Fig. 1, 3a, 3b), die dikwijls werd geïsoleerd, wordt beschreven als nieuwe soort en de relatie met anderePythium-soorten met gestekelde oögoniën wordt besproken. In proeven bleekP. uncinulatum zeer pathogeen te zijn voor zaailingen van sla en iets minder voor zaailingen van komkommer en tomaat (Fig. 4a, Tabel 2). Het planten van slazaailingen in metP. uncinulatum geïnoculeerde grond had meer effect dan het dopen van de wortels in een myceliumsuspensie van de desbetreffende schimmel vóór het planten. Het effect uitte zich in groeivertraging van de plant en beschadiging (necrose) van het gehele wortelstelsel. P. tracheiphilum (Fig. 2, 3c), die slechts een paar maal werd geïsoleerd, was zeer pathogeen voor zaailingen van sla, komkommer en bloemkool (Fig. 4a) en iets minder voor zaailingen van tomaat en erwt (Tabel 2). Groeiremming van de planten was sterker wanneer de wortels van de zaailingen vóór het planten in een myceliumsuspensie vanP. tracheiphilum gedoopt werden (Fig. 4b), dan wanneer de zaailingen in geïnoculeerde grond geplant werden. De hoofdwortels van de zaailingen werden ernstig beschadigd, maar zich later vormende zijwortels werden weinig door de schimmel beïnvloed.Tot nu toe zijn de pathogeniteitsproeven slechts met zaailingen uitgevoerd. Proeven met volwassen planten moeten volgen om te onderzoeken of er een verband kan bestaan tussen de aanwezigheid van de betreffendePythium-soorten in de grond en het optreden van smet in sla.     

肉桂后半啮的生物学特性及其防治

肉桂后半啮是桂皮产品的主要仓储害虫,在广东１ａ发生３～４代,世代重叠。以成虫在土壤缝隙中越冬,翌年３月下旬开始产卵,完成一代约４５～５５ｄ。每年６～７月是肉桂后半啮发生危害的高峰期,采用常规清洁措施结合药物防治效果较好。     

Some studies on the competition between Avenu fatua L. and spring barley.II. Variation of A. fatua emergence and development and its influence on crop yield.

The emergence and development of A fatua were studied in 23 spring barly fields in 1972 and nine in 1973 nautarally infested with yhe weed. Emergence occurred up to the four-leaf stages of the crop. The mean number of days from drilling to 50% emergence of A fatua plants was 22 in 1972 and 36 in 1973.The majority of seeds were shed by early emerging plants in 1972, 79% and in 1973. 59% of A fatua plants had emerged by the two-leaf stage of the crop and these plants produced 97 and 89% respectively of all the seed shed. In both years, A fatua plants emerging before the crop produced five times as many seeds per plant as those emerging between the crop two and three-leaf stages. The earliest emerging plants were also the heaviest and had most stems per plant.In both years there was a significant relationship between the density of A fatua plants in the crop in spring and their mortality.A large variation occured between the sites in the number of A fatua plants that emerged by a given crop leaf stage. In 1973.insufficient numbers of sites were investigatesd to derive a relationship between time to A fatua emergence and crop yield loss, but in 1972, a given density of A fatua plants emerging at an early stage caused agreater crop yields loss than the same density emerging later. This was also evident to aleser extent in data derived from a similar series of 15 experiments in 1971.